Brake



K. M. YOST July 7, 1942.

BRAKE Filed May 1, l94 0 2 Sheets-Shag: 2

N VBN TOD l crr/ 5 0575 filwomkys PatentedJuIyY,

masses Kari M. Yost, Beloit, Wia, auignor to Warner Electric Brake Manufacturing Company, South Beloit, 111., a corporation of Illinois application May l, 1940, Serial no. 332,711

'* 8cm lac-106i This invention relates generally to friction brakes of the character used on automotive vehicles and more partlc'ularly'to a brake of the type in which the-retarding eiIect is augmented by a wrapping or self-energizing action that is created when the brake is applied.

One object. of invention is to provide a brake oi the above general character in which v the wrapping action is built up within a plurality of independent lriction elements and therebyutilized to augment the total retarding bolted to the vehicle wheel or other part to be bruised and havingan internal cylindrical surface adapted to be gripped by non-rotatable friction means supported by an anchor plate 1 which closes the open end of the drum and is carried by an axle housing or other non-rotatable part. The irlction means comprises two seml-circu-f lar shoes 8 either flexible or rigid arranged in.

end to end relation within the drum to anchor at either end so as to produce a self-energizing or wrapping action whenone end is moved cireifect while at the same time being maintained The invention also resides in the novelv construction'ot n1; trictionelements, of the aux-' iliary operator,. and the arrangement or return springs by whichthe elements are normally held in released positions.

Other objects and advantages 0! tion will become apparent from the following detailed description taken in connection with the accompan9ing in which oiFig;l. r

Fig.3 is a fragmentary sectional view taken along the linel-l '2.

Figs. 4 and aref sec'tions taken=along the lineal-4 and t-esg r Fig. 1.

cumterentially. As shown, each shoe comprises a curved band or plate 9 having a segment ili oi'suitable trictionmaterial riveted or otherwise secured to its outer surface. "Elongated lugs 21-, welded along the center line of the shoe hands 9 are received in guide notches 28 on brackets '29 which are rigid with the anchorv'plate. and hold the shoe against lateral movement while permitting otthe longitudinal movement .incldent to expansion of the shoes within the Extending along the longitudinal center lines 1 and welded to the ends of the plates 9 as indicated at 8'- are brackets ii which'relnforce the inven-' Figure 1 is a-Iragmentary diametrical sectional view of a' brake the novel teatures or the present iriveritiomthelaectionib taken along the line ii 01 1 .2( f

Fig.2 is asection along the line 2-4 Fig. 6 is apfragx'nentary perspective view of I one of the brake 1 While the inventionis susceptibleo! various modifi-cations and alternative constructions, I

have shown infthedrawings and will herein describe in detail the preferred embodiment. It is to be understood, however, that I do not intend 'to limit the invention by such disclosure but aim to cover all modifications and alternative constructions tailing-within the spirit and scope of 1 the invention as expressed in the appended claims. r 1

The brakeis oi the internal expanding type comprislnga drum I with an lnturned flange l shoe ends and have heads I! projecting beyond the shoe ends.

fitting around and;bearing against the outer cylindrical surfaces of anchor pins i4 and it. .I'he pin i4 projects through the anchor plate and bosses ilinto the drum parallel to the axis or the latter, being made rigid with'the anchor plate by welds ii. For a purpose to appear later, the anchor pin it is Journaled in a bushing i8 projecting parallel to the drum axis through the periphery of the anchor plate and plates is to which the bushing is made rigid asby welds 20.1

The shoe ends arelheld on their anchors by plates Ii received on the reduced ends 22 oi. the

anchors and fastened by spring washers 23. The.

ends I or the plates litare .bent either toward or away i'rom theanchor. plate to bring them as close as possible to the longitudinal center lines oi the shoes 8.; Between these ends and lugs 25 on the inner sides or the shoes are stretched contractile springs 28. It will Benoted that the lines 'of action of these retumsprlngs are through the" centers ot'the anchor plus I! and II as a ,result or which each shoe end is always guided back against its anchor .pln with the latter seating correctly in the-end surface II.

a The shoe ends are termed with abutment surfaces}! which extend parallel to but are spaced a short distancefrom a. diameter-30' -ss' -tnmush the anchor axes. m the contracted These heads have end recesses. defined by concave and semi-circular surfaces It positions of the shoes (Fig. 1), these surfaces, which it will bepbserved are in the plane of n the anchoringsurfaces I3 and also of the longiplates l6 and 2| by which it is positioned axially.

In the other, it is turned on the pin l and also is counterbored as indicated at 34 to receive the reduced end 35 of the bushing l8 to provide ample bearing area. 7

When the crank arms are swung-in either direction away from normal brake-released position shown in Fig. 2, the lugs 3| move in the same direction and each engages one of the abutments 30 thereby shifting the adjacent shoe ends circumferentially "away from the anchor pins. .Since the opposite ends of the shoes remain anchored on these respective pins, such circumferential movement results in expansion of the shoes within the drum. If, as is desirable, the actuated ends are moved in the direction of drum rotation, engagement of the shoe surfaces with the drum will initiate a wrapping or selfenergizing action that builds up throughout the length of each shoe so that the retarding effect due to the actuating force applied to the crank arms 33 will be augmented several times. Owing, however, to the fact that the friction surface is'divided-into separate annularly spaced'ele ments or shoes and each part extends less than halfway around the drum, the so-called wrap factor is limitedin magnitude and the total retarding effect is kept within controllable limits. This action is also rendered more uniform and controllable because the anchored shoe ends, owing to the tongue and groove connection with the anchor pins, are held against radial movement and thereby always occupy the same position under all conditions. Thus, as an incident to expansion, the anchored shoe ends pivot about the pins and the shoes flex into full contact with the drum surface.

In the present instance, the brake is adapted to be' applied by either of two independently operable actuators. One of these is a power operator of themomentum type which moves one end or the other of each shoe selectively in the direction of rotation of the drum and exerts the actuating force through both of the levers 33 by which the force is amplified approximately four times. As shown herein, the operator includes an annular'magnetic ring 38 mounted to oscillate about the drum axis on bearings 31 carried by segments 38 of angular cross-section. The

-- latter provide backing 39 for the magnet and are rigidlysupported from the anchor plate I through the medium of a block 40. The magnet is held on the segments loosely against the 'backings 39 by fingers 50 (Fig. 3) projecting free ends of the crank arms 33 which ends are offset toward the anchor plate to permit of such location of the lugs. The lugs of each pair are spaced apart and receive between them a roller 46 rotatably supported by and projecting laterally from the free end of one crank arm 33. The connection thus provided between the magnet and the crank arms enables a substantial leverage to be obtained and provides for movement of the shoe endsin the proper direction to create the desired self-energizing action irrespective of the direction of rotation of the drum at the time the brake is applied.

Coiled contractile springs 41 are anchored at one end of one bracket 29 and at their other ends arehooked through and slidable along elongated eyes 48 on the outer surface of the magnet ring. These springs act in opposite directions on the magnet ring and thus tend to return the ring to and maintain it in the normal brake-released position .shown in Fi 2 while at the same time permitting the ring to move in either direction away from this position. In the released position, the shoes are contracted against their anchor pins l4 and I5 by the springs 26 and the levers 33 project inwardly along a diameter of the drum through the lever pivots.

Energization of the magnet winding 49 produces a proportional gripping engagement between the' rotating armature and the friction face of the magnet ring causing the magnet to turn with the armature. This movement is communicated through one lug 45 of each pair to the rollers 46 which ride outwardly along the lugs as the free ends of the crank arms 33 move with the magnet. The lugs 3|, since they project from the lever pivot in the same direction as.

the crank arms, move in the direction of drum rotation and shift one end of each shoe away from its anchor pin depending on the direction of drum rotation (see Fig. 4). This results in expansion ,of the shoes and initiation of the self-energizingaction to create a powerful braking effect in the manner described above. After the clearance between the shoes and the drum has been taken up, slippage occurs between the magnetand armature faces until the wheel stops revolving, the brake being held set so long as l the magnet remains energized. When the magnet winding is deenergized, the springs '26 and 41 coact'to return the shoes and the magnet to released position.

With an actuating andanchoring mechanism jacent shoe ends, it will be observed that only one end of each shoe will be actuated while the other end anchors. Thus, the actuated end of each shoe is always the trailing end with reference to the direction of drum rotation so that the latter determines which shoe ends will be actuated during each brake application. As a result of this, each shoe constitutes the seat of a self-energizing action by which the applied actuating force is augmented substantially. Since each shoe oc cupies less than half of the drum. circumference,

the self-energizing action is maintained within controllable limits and the expansive forces exerted on the drum are well balanced. Also, by

dividing the actuating force, that is, by connecting the separate shoe actuators to the magnet ring at points spaced uniformly'around the ring,

the forces applied to the ring bearing are substantially balanced and there is little tendency for the ring to bind on'its mounting: Moreover, the actuating and reactionary forces incident to Iii-l applicationof the brake are directeddn the-plane of the'shoe center lines. Such advantageous division and balancing of the forces involved minimize the unit stresses on the bearings and on the actuating and anchoring parts, enabling'construction costs to be maintained at a minimum while at the same time insuring reliability in operation and durability in service. i

The second or auxiliary actuator. is intended for use for parking or under emergency conditions and is operated manually. It'inciudes the anchorpin I! which for this purpose is rotatable betwee the lug 3i and the retaining plate 2|.

Lobes t projecting m diametrically opposite directions from the periphery of the disk have surfaces 5i that bear against the end faces 58 on lugs 59 rigid with and projecting laterally from the heads it of the shoe brackets H at points spaced fromthe shoe ends 30 so as toavold weal:- ening of the cam disk due to the presence of the slot 5t. The'radial lengths of the surfaces 53 and the lobes Eb are'determined by the maximum allowable shoe clearance.

When the shaft i5 is rocked counterclockwise as viewed in Fig. 5, the lobes 58 cam the lugs 'bt apart, thereby moving both shoe ends away from the anchor in Since the opposite ends anchor on the pin it, the, shoes are expanded and the brake applied producing a retarding effect proportional to the actuating force manuaily applied Because the slot 54 is longer than the flattened shaft end 53 and extends generally transversely of a drum diameter through the cam axis, the cam is free to shift on the end 53 generally circumferentially of the drum and along the line of shoe end. movement. Such movement will occur under the reactionary forces exerted bythe shoes if the friction surfaces of the two shoes have worn unevenly. This is apt to be the case because the brake will normally be applied morefrequently with the vehicle traveling forwardly. Dlflerential wearing of the shoe ends is thus compensated for automatically and does not detract from the effectiveness of the auxiliary brake actuator. The latter, it will be assesses supported by said shaft and engageable with one or the other ofsaid ends to move such end circumferentially away from the shaft, and a cam on said shaft and ,engageable with both of said ends to spread the latter apart and away from their anchors when the shaft is turned away from brake-released position.

2. A brake having, in combination, a rotatable drum, an expansible friction element extending around the internal drum surface and having adjacent separableends, a rotatable shaft disposed between said ends and projecting parallel to the drum axis, said shaft providing an anchor forsaid ends, and two levers, one being loose on said shaft and operable selectively to actushaft providing an anchor for said ends, a crank arm rotatably supported by said shaft and ,hav; ing an eccentric lug engageable with one or the other of said ends to move the latter circumferentially, abutments on said shoe ends facing said shaft, and acam on said shaft engageable with said abutments to spread the shoe ends apart when the shaft is turned'away from brakereleased position. a

4. A brake comprising a rotatable drum, a plurality of shoes arranged in end to-end relation around the internal surface of said an abutment anchor for each pair of adjacent shoe ends, a main actuator operator associated with each pair of said ends and operable se lectively according to the direction of drum ruobserved, moves both band ends away from the dicular to this diameter (see Fig. 5) as an incl-- dent to turning of the cam to expand the brake. As a result, the freedom with which the disk is adapted to shift increases as the cam turns to expand the shoes andis a maximum whenthe shoes are .fully expanded-and the slot 54 thus extended tangentially as shown in Fig. 5.

I claimJas my invention:

a 1. A brake/having, in "combination, a'rotat- "ablefdrum, an expansiblefriction element ex- '1 tending around the internal drum surfaceand having adjacent separable ends, a rotatable shaft disposed between said ends. and projecting partation to move the trailing end only of each shoe circumferentially away from the respective anchors, and an auxiliary operator including an expanding cam associated with only one of said pairs of shoe ends and operable to spread both of such ends apart and away from their anchors while the opposite ends of the shoes remain in abutment with their anchors.

5. A brake. having, in combination, a rotatable drum, an anchor plate, a friction element extending around the internal drum surface with its ends disposed adjacent each other, a: shaft iournaled in saidanchor plate and disposed between said ends, a sleeve loose on. said shaft, an arm rigid with said sleeve and engage-= able with said ends to expand said element upon swinging or the arm in either direction from a normal brake released position, and an auxiliary actuator carried by said shaft and operableto expand said elementupon turning of the shaft away from a normal brake released position.

6. A brake having, in combination, a rotatable drum, a plurality ofshoes arranged end to end around the internal drum surface, rigid members eachprojecting between the adjacent. ends of different shoes and providing oppositely fac ing abutments against which the respective ends anchor, a momentum type operator including a driven element movable frictionally in one direction or the other when theoperator is activated, the direction of suchmovement corresponding to the direction of rotation of said drum, arms mounted to swing on fixed axes disallel-to the drum axis, said shaft providing an posed between the adjacent shoe ends with their free ends projecting inwardly, means connecting said free ends with said element for movement therewith, and means 'on the respective arms and engageabie selectively with the trailing ends only of said shoes when said element is moved in either direction and operableuto move such ends away from their anchors, the

leading shoe ends, as determined by the direction oi! drum rotation, remaining against their anchors during such movement of said element.

'7. A brake having, in combination, a rotatable drum, an expansible iriction element extending around the internal drum surface with its ends disposed adjacent each other, each of said ends having'inner: and outer abutments spaced radially of the drum, a member disposed betweenand engageable with the outer abutments to anchor one of said ends or the other depending on the direction oi rotation of said drum when'said element is expanded, an inwardly projecting arm swingable in opposite directions about a fixed axis disposed between said 8. A brake having, in combination, a rotatable drum, expansible friction means within the drum, an actuating ring smaller than said friction means, a crank pivoted adjacent the internal drum surface and operable to expand said friction means, the free end of said crank projecting radially across said ring, means rigid with said ring and projecting radially inwardly therefrom, and means connecting said free end with said last mentioned means at a point spaced inwardly from the ring, said connecting means providing for actuation of the crank by turning of the ring.

ends and extending parallel tothe drum axis,

KARL M. YO ST. 

